The Rabbinical Assembly, the1,200-member body of the nation's Conservative rabbinate, has adopted a resolution calling for an immediate freeze by the Soviet Union and the United States on development and deployment of all nuclear weapons.

The resolution of the assembly, representing the largest branch of Judaism in this country, also urged the United States and the Soviet Union to "vigorously pursue the next round" of strategic arms limitation talks aimed at reaching a "mutually verifiable" agreement to reduce the nuclear arsenals of both nations.

In another action at its annual meeting held last month in Kiamesha Lake, N.Y., the assembly voted to begin a campaign against smoking. The antismoking resolution noted the dangers to health posed by tobacco, called for efforts in local congregations to sensitize members to this problem, pledged support of civil smoking bans in public places, and banned smoking at future assembly meetings.

"Jewish ethics and Jewish law would prohibit the use of cigarettes," Rabbi Seymour Siegel of the Jewish Theological Seminary told the assembly. "Smoking should at least be banned in synagogues, Jewish schools and in Jewish gathering places."

Rabbi Arnold M. Goodman of Adath Jeshurun Congregation in Minneapolis was elected president of the assembly. In addition to his rabbinical training, Goodman holds a law degree from DePaul University and, during a sabbatical year in Israel a decade ago, qualified as a member of the Israeli Bar Association.

The Conservative rabbis, concerned about Orthodox Judaism's monopoly of religious practice in Israel, vowed to step up their efforts for recognition in Israel of their more contemporary interpretation of Judaism. Currently, neither Conservative nor Reform Judaism is recognized in Israel, and rabbis of those two expressions of Judaism are not authorized to perform such rites as officiating at marriages.

The action of the Conservative rabbis came as the Israeli-owned airline, El Al, announced plans to accede to demands of Agudat Israel, the ultra-Orthodox religious party, to shut down operations on Saturdays, the Jewish sabbath, and on Jewish religious holidays.

Agudat Israel has long charged that El Al was desecrating the Sabbath by its Saturday operations. Closing down the airline on Saturdays was one of 83 conditions that Agudat Israel set as the price of cooperation in the 1981 coalition government of Menachem Begin.

El Al management has protested that in would cost the airline between $40 million and $70 million to close down on Saturday as Agudat Israel has demanded. Saturday passengers--largely Christian pilgrims--currently make up 24 percent of the airline's passenger business. Loss of this much business, plus additional expenses of housing its planes and flight crews in foreign airports during the Sabbath hiatus, is expected to be a serious financial blow to the airline.